3-(phenyl)-3-(indol-3-yl)-phthalides



Jan. 20, 1970 AQ-HAN 3,491,116

5-(PHENYL)-'5-( IlIDOL--$--YL) -PHTHALIDE3 Filed Jan. 59, 1967 FIG. I

BASE-SHEET OF RECORD MATERIAL COATED ON THE REAR WITH MINUTEPRESSURE-RUPTURABLE CAPSULES CONTAINING LIQUID SOLUTION OF CHROMOGENICMATERIAL DEVELOPABLE ON CONTACT WITH AN ELECTRON- ACCEPTING MATERIAL OFTHE LEWIS- ACID TYPE TO COLORED FORM.

RECEIVING SURFACE OF UNDERSHEET COATED WITH AN ELECTRON-ACCEPTINGMATERIAL OF THE LEWIS-ACID TYP INVENTOR CHAO-HAN LIN HIS ATTORNEYSUnited States Patent 3,491,116 3-(PHENYL)-3-(INDOL-3-YL)-PHTHALIDESChao-Han Lin, Dayton, Ohio, assignor to The National Cash RegisterCompany, Dayton, Ohio, a corporation of Maryland Filed Jan. 30, 1967,Ser. No. 612,459 Int. Cl. (107d 99/04; B411 1/36 US. Cl. 260-32614 8Claims ABSTRACT OF THE DISCLOSURE A novel chromogenic material ofnormally colorless form, having a structural formula:

wherein R and R comprise alkyl radicals having from one to five carbonatoms, aryl radicals, and hydrogen; and R and R comprise alkyl radicalshaving from one to five carbon atoms and hydrogen; said materialassuming a colored form upon contact with a Lewis acid molecule.Examples include This invention pertains to novel chromogenic com poundsfor use in pressure sensitive record material and to an improvedmark-forming manifold system incorporating these novel chromogeniccompounds. More specifically, this invention pertains to3-dialkylaminophenyl-3- indolyl phthalides which have the form ofsubstantially colorless, i.e. white, or slightly colored solids, orapproach being colorless when in liquid solution, but which may beconverted to dark-colored forms upon reactive contact with acidicmaterial. As used in mark-forming systerns, marking in desired areas onsupport webs or sheets may be accomplished by effecting localizedreactive ,contact between the chromogenic material and the acidicmaterial on or in such a web or sheet, such material being broughtthereto by transfer, or originally there in situ, the desired reactivecontact forming dark-colored materials in the intended image areas.

Pressure-sensitive, mark-forming systems of the prior art include thatdisclosed in application for Letters Patent No. 392,404, filed Aug. 27,1964, by Robert E. Miller and Paul S. Phillips, Jr., and now abandoned.The latter application provides a marking system of disposing on and/ orwithin sheet support material the unreacted markforming components (atleast one of which is a polymeric material) and a liquid solvent inwhich each of the markforming components is soluble, said liquid solventbeing present in such form that it is maintained isolated by apressure-rupturable barrier from at least one of the markformingcomponents until the application of pressure causes a breach or ruptureof the barrier in the area delineated by the pressure pattern. Themark-forming components thereby are brought into reactive contact,producing a distinctive mark.

It is an object of this invention to provide new and improved substanceshaving chromogenic properties which may be incorporated in a web orcoated onto the surface of a web to provide a novel manifolding unit,and which are useful in carrying out improved methods of markinginvolving reactive contact with a color-activating material to developdark-colored materials in areas where marking is desired.

It is another object of this invention to provide modified compounds,based upon the 3-(p-dialkylaminophenyl)-3-indolyl phthalides, which aresubstantially colorless, or slightly colored offering a new and improvedvariety of chromogenic characteristics, and developing noveldark-colored substances upon contact with coloractivating materials.

It is a further object of this invention to provide a new and improvedmark-forming system which has the form of disposing within a web or uponthe surface of a web or sheet support material unreacted chromogenicmaterial which is capable of being reactively contacted with an acidicmaterial to produce a dark-colored substance, thus providing markshaving desirable color intensity and hue.

In accordance with this invention, there is provided a novel,substantially colorless or slightly colored, chromogenic compound havingthe structural formula:

wherein R and R comprise alkyl radicals havingfrom 1 to 5 carbon atoms,aryl radicals, and hydrogen; and R and R comprise alkyl radicals havingfrom 1 to 5 carbon atoms and hydrogen. Examples of these novel compoundsare 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl) phthalidehaving the structural formula:

3 3 (p dimethylaminophenyl) 3 (2 methylindol 3- yl) phthalide having thestructural formula:

3 (p di n b utylaminophenyl 3 (1,2 dimethylindol-3-yl) phthalide havingthe structural formula:

3-(p-di n butylaminophenyl)-3-(2-methylindol-3-yl) phthalide having thestructural formula:

CH I

3 (p dimethylaminophenyl) 3 (2-phenylindol-3-yl)3-(p-dimethylaminophenyl)-3-(1-methyl-2 phenylindol- 3-yl) phthalidehaving the structural formula:

3 (p diethylaminophenyl) 3 (2 phenylindol-S-yl) phthalide having thestructural formula:

I 20 Al}; N 7 O In accordance with another feature of this invention anew composition of matter comprises the dark-colored substance having aresonant form developed by contact of a color-activating material withone of the above-mentioned chromogenic compounds. The color-developingor activating material is an acidic substance for converting thechromogenic compound to the resonant form.

The method of marking of this invention, i.e., by developing adark-colored material from substantially colorless or slightly coloredchromogenic compounds comprises providing a chromogenic compoundselected from among the above-mentioned compounds and bringing suchchromogenic compound into reactive contact in areas where marking isdesired with an acidic color-activating substance to produce adark-colored resonant form of the chromogenic compound by the actionthereon in said areas of the said acidic substance.

The acidic materials employed in this invention can be any compoundwithin the definition of a Lewis acid, i.e., an electron acceptor.Preferably, acidic organic polymers such as phenolic polymers areemployed as the acidic material. The novel chromogenic materials exhibitthe advantage of improved color stability when reacted with suchphenolic polymers. The solution formation of the solid particles ofpolymeric material in the same solvent with the substantially colorlesschromogenic compounds allows penetration of the color into the supportsheet, if porous,-e.g., paper, so that the colored form of thechromogenic material sinks into the body of the sheet and is not merelyon the surface of the sheet. This feature protects against erasure ofrecorded data by attrition of the surface of the record sheet.

Reference is directed to the drawings. FIGURE 1 is a diagrammaticrepresentation of a two-sheet unit manifold, a perspective in which thebottom surface of the overlying is supplied on the surface or near itwith a multiplicity of minute pressure-rupturable microcapsules, eachcontaining a droplet. Each droplet contains a solution of the basicchromogenic component. An acidic component, such as an acid clay or aphenolic polymeric material lies Within the lower web or sheet or uponthe upper surface of the lower Web or sheet. A colored mark is made bythe use of a stylus, a type character, or other pressure-writing meansapplied to the two-sheet unit manifold.

The encapsulated droplets are released on the rupture of the capsules inwriting operations, as shown in FIGURE 10!. The liquid of the releaseddroplets is transferred in the pattern of the data configuration to thetop of the underlying sheet. The top of the underlying sheet is coatedor impregnated with a material reactant with the chromogenic material,e.g., a phenolic polymer material having an acid-reacting OH group. Thedrawings show capsules on the over-sheet containing a liquid solution ofchromogenic material. However, the capsules can contain the polymericphenolic material in liquid solution and the top surface of theunder-sheet may be supplied with the chromogenic material in particulateform. The improvement in the system is the chromogenic compound which isthe novel substance of the instant invention.

Referring again to FIGURE 1 comprising an upper web or sheet having thechromogenic material dispersed within or upon in a contiguousjuxtaposition, it is possible to incorporate the chromogenic material ina solid, crystallinestate in a binder material so that the chromogenicmaterial may be transferred from the upper Web or sheet upon theapplication of pressure from a stylus to deposit some of the chromogenicmaterial on a surface carrying a color activating polymeric material.Preferably, the chromogenic substance is dissolved in a solvent andminute droplets of the solution of the chromogenic material areencapsulated in minute, rupturable capsules. Obviously, many otherarrangements, configurations and relationships of the solvent and themark-forming materials, with respect to their encapsulation and locationon the supporting sheet or webs can be envisioned. Such arrangements arethoroughly described in the aforementioned application Ser. No. 392,404to Miller et al., and need not be repeated herein.

It is noted that the polymeric mark-forming components should have acommon solubility with the chromogenic material in at least one liquidsolvent when the acid-reacting material is a phenolic or other organicacidic polymer. It is also noted that in a single system severalchromogenic materials may be used with the same or different polymericmaterials. Several polymeric materials can be reactively contacted Witha single chromogenic compound or with a mixture of chromogeniccompounds.

As mentioned above, the solvent is maintained in physical isolation inminute droplets until such time as it is released by application ofpressure. This may be accomplished by several known techniques, butpreferably isolation is maintained by individual encapsulation of thesolvent droplets in a microcapsule according to the proceduresdescribed, for example, in U.S. Patent No. 2,712,507, issued to BarrettK. Green on July 5, 1955; 2,730,457 issued to Barrett K. Green andLowell Schleicher on Jan. 10, 1956; 2,800,457, issued to Barrett K.Green and Lowell Schleicher on July 23, 1957; and 2,800,458, issued toBarrett K. Green on July 23, 1957, reissued as Reissue Patent No. 24,899on Nov. 29, 1960. The microscopic capsules, when disposed within or upona supporting web as a multiplicity in contiguous juxtaposition, arerupturable by pressure, such a normal marking pressures utilized, forexample, in writing or typing operations.

The material or materials chosen as the wall material of themicrocapsule, in addition to being pressure rupturable, must be inert orunreactive in respect to the contents of the capsule and the othermark-forming components so that the wall material remains intact undernormal storage conditions until such time as it is released by theapplication of marking pressure. Examples of such wall materials aregelatin, gum arabic and many others thoroughly described in theaforementioned patents.

For use in record material, the capsule size should not exceed 50microns in diameter. Preferably, the capsules should be smaller thanmicrons in diameter.

The acidic organic polymeric material useful in this invention includephenolic polymers, phenol acetylene polymers, maleic acid-rosin resins,partially or wholly hydrolyzed styrene-maleic anhydride copolymers andethylene-maleic anhydride copolymers, carboxy polymethylene and whollyor partially hydrolyzed vinyl methyl ether maleic anhydride copolymerand mixtures thereof.

Phenolic polymers found useful include alkyl-phenolacetylene resins,which are soluble in common organic solvents and possess permanentfusibility in the absense of being treated by cross-linking materials. Aspecific group of useful phenolic polymers are members of the typecommonly referred to as novolacs (as sold by Union Carbide Corp., NewYork, N.Y.), which are characterized by solubility in common organicsolvents and which are, in the absence of cross-linking agents,permanently fusible. Generally, the phenolic polymer material founduseful in practicing this invention is characterized by the presence offree hydroxyl groups and the absence of groups such as methylol, whichtend to promote infusibility or cross-linking of the polymer, and bytheir solubility in organic solvents and relative insolubility inaqueous media. Again, obviously, mixtures of these organic polymers andother acidic materials can be employed.

Resoles, if they are still soluble, may be used, though subject tochange in properties upon aging.

A laboratory method useful in the selection of suitable phenolic resinsis the determination of the infra-red absorption pattern. It has beenfound that phenolic resins showing an absorption in the 3200-3500 cm?region (which is indicative of the free hydroxyl groups) and not havingan absorption in the 16004700 cm. region are suitable. The latterabsorption region is indicative of the desensitization of the hydroxylgroups and, consequently, makes such groups unavailablefor reaction withthe chromogenic materials.

The preparation of organic polymeric materials for practicing thisinvention is described in Industrial and Engineering Chemistry, vol. 43,pages 134 to 141, January 1951, and a particular polymer thereof isdescribed in Example I of U.S. Patent No. 2,052,093, issued to HerbertHonel on Aug. 25, 1936, and the preparation of the phenol-acetylenepolymers is described in Industrial and Engineering Chemistry, vol. 41,pages 73 to 77, January 1949.

The preparation of the maleic anhydride copolymers is described in theliterature, such as, for example, one of the maleic anhydride vinylcoploymers, as disclosed in the publication, Vinyl and Related Polymers,by Calvin E. Schildknecht, second printing, published April 1959, byJohn Wiley & Sons, Incorporated. See pages to 68 (styrene-maleicanhydride copolymer), 628 to 630 (vinyl methyl ether-maleic anhydridecopolymer), and 530 to 531 (ethylene-maleic anhydride copolymer).

When the acidic material is one of the aforementioned organic polymers,the liquid solvent chosen must be capable of dissolving the mark-formingcomponents. The solvent may be volatile or non-volatile, and a single ormultiple component solvent may be used which is wholly or partiallyvolatile. Examples of volatile solvents useful in the afore-describedbasic chromogen-acidic polymer are toluene, petroleum distillate,perchloroethylene, and xylene. Examples of non-volatile solvents arehigh-boiling point petroleum fractions and chlorinated biphenyls.

Generally, the solvent chosen should be capable of dissolving at least0.3%, on a weight basis, of the chromogenic material, and about a 3-5 ona weight basis, of the polymeric material to form an eflicient reaction.However, in the preferred system, the solvent should be capable ofdissolving an excess of the polymeric material, so as to provide everyopportunity for utilization of the chromogenic material and, thus, toassure the maximum coloration at a reaction site.

A further criterion of the solvent is that it must not interfere withthe mark-forming reaction. In some instances, the presence of thesolvent may interfere with the mark-forming reaction or diminish theintensity of the mark, in which case the solvent chosen should besulficiently vaporizable to assure its removal from the reaction siteafter having, through solution, brought the markforming components intointimate admixture, so that the mark-forming contact proceeds.

Since the mark-forming reaction requires a intimate mixture of thecomponents to be brought about through solution of said components, oneor more of the markforming components may be dissolved in the isolatedsolvent droplets, the only requirement being that at least one of thecomponents essential to the mark-forming reaction be maintained isolateduntil reactively contacted with the other.

In the usual case, the mark-forming components are so chosen as toproduce a mark upon application of pressure at room temperature (20 to25 degrees centigrade). However, the present invention includes a systemin which the solvent component is not liquid at temperatures around roomtemperature but is liquid and in condition for forming solutions only atelevated temperatures.

The support member on which the components of the system are disposedmay comprise a single or dual sheet assembly. In the case where allcomponents are disposed on a single sheet, the record material isreferred to as a self-contained system. Where there must be a migrationof the solvent, with or without mark-forming component, from one sheetto another, the record material is referred to as a transfer system.(Such a system may also be referred to as a two-fold system, in that atleast two sheets are required and each sheet includes a component, orcomponents, essential to the mark-forming reaction.) Where a copiousamount of the colored reaction product in liquid form is produced on asurface of one sheet, it may produce a mark by transfer to a secondsheet as a colored mark.

In the preferred case, where microcapsules are employed, they may bepresent in the support material either disposed therethroughout or as acoating thereon, or both. The capsules may be applied to the sheetmaterial while still dispersed in the liquid vehicle in which they weremanufactured, or, if desired, separated and the separated capsulesthereafter dispersed in a solution of the polymeric component (forinstance, 30 grams of water and 53 grams of a 1% aqueous solution ofpolyvinyl methyl ether maleic anhydride) to form a coating compositionin which, because of the inertness of the solution and the capsules,both retain their identity and physical integrity. When this compositionis disposed as a film on the support material and dried, the capsulesare held therein subject to rupture to release the liquid contained.This latter technique, relying on the inertness of the microcapsule andthe dispersing medium of the film-forming markforming component, allowsfor a method of preparing a sensitive record coating with the capsulesinterspersed directly in a dry film of the polymeric material as it islaid down from the solution. A further alternative is to disperse in aliquid medium one or more mark-forming components, insoluble therein,and disperse in said medium the insoluble microcapsules, with the resultthat all components of the mark-forming system may be disposed on orWithin the support sheet in the one operation. Obviously, the severalcomponents may be applied individually.

The respective amounts of the several components will vary, dependingprimarily upon the nature of the materials and the architecture of therecord material unit. Suitable lower amounts include, in the case of thechromogenic material, about .005 to .075 pound per ream (a ream in thisapplication meaning five hundred (500) sheets of 25" x 38" paper,totalling 3,300 square feet); in the case of the solvent, about 1 to 3pounds per ream; and in case of the polymer, about /2 pound per ream. Inall instances, the upper limit is primarily a matter of economicconsideration.

In the instance where the mark-forming components are interspersedthroughout a single support sheet material (so-called self-containedunit), the following technique or procedure has been found useful:

The slurry of capsules may be applied to a wet web of paper as it existson the screen of a Fourdrinier paper machine, so as to sink the paperweb a distance depending on the freeness of the pulp and the watercontent of the web at the point of application.

The capsules may be placed directly in the paper or in a support sheet.Not only capsule structures, but films which hold a multitude ofdroplets for local release in an area subject to pressure may beutilized. (See US. Patent No. 2,299,694 which issued Oct. 20, 1942, toB. K. Green.)

With respect to the acidic organic polymeric component, a solutionthereof in an evaporable solvent is introduced into twice as much waterand agitated while the evaporable solvent is blown off by an air blast.This leaves an aqueous colloidal dispersion slurry of the polymericmaterial, which may be applied to the paper so as to leave a surfaceresidue, or the slurry may be applied to paper at the size-press stationof a papermaking machine by roller. In another method of making apolymersensitized sheet, the water-insoluble polymer is ground to thedesired particle size in a ball mill with water, preferably with adispersing agent, such as a small quantity of sodium silicate. If abinder material of hydrophilic properties is ground with the phenolicmaterial, the binder itself may act as a dispersant. If desired, anamount of binder material of up to 40%, by weight, of the employedamount of the polymeric material may be added to the ball-milled slurryof materials, such binder materials being of the paper coating binderclass, including gum arabic, casein, hydroxyethylcellulose, and latex(such as styrene-butadiene copolymer). If desired, oil adsorbents in theform of fullers earths may be added to the polymeric material particlesto assist in retaining, in situ, the liquid droplets to be transferredto it in data-representing configuration, for the purpose of preventingbleeding of the print.

Another way of applying the chromogenic or polymeric materialindividually to a single sheet of paper is by immersing a sheet of paperin a 1% to solution of the material in an evaporable solvent. Obviously,this must be done alone for each reactant, because if the other reactantmaterial were present, it would result in a premature coloration overthe sheet area. A dried sheet with one component then may be coated witha solution of the other component, the solvent of which is a non-solventto the already supplied component.

The polymeric material may be dissolved in ink composition vehicles toform a printing ink of colorless character and, thus, may be used tospot-print a proposed record sheet unit sensitized for recording in areactionproduced color in those areas by application of a solution ofthe chromogenic material.

In the case of phenolic polymer, a printing ink may be made of up to 75%weight, of the phenolic polymeric material in a petroleum solvent to aviscosity suitable for printing purposes. The relative amounts ofcomponents to be used are the most convenient and economical amountsconsistent with proper visibility of the recorded data. The resolutionof the recorded data is, among other things, dependent on particle size,distribution and amount of particles, liquid solvent migration, chemicalreaction efficiency, and other factors, all of which are things that maybe worked out empirically by one familiar with the art, and which do notdetermine the principle of the invention, which, in part, involves meansfor enabling the bringing into solution, by marking pressure, of twonormally solid components in a common liquid solvent component heldisolated as liquid droplets, preferably in marking-pressure-rupturablecapsules having film walls, or else held isolated in a continuousmarking-pressurerupturable film as a discontinuous phase.

In the base-acid color system of this invention the acidic mark-formingcomponent'(s) reacts with the basic chromogenic material(s) to effectdistinctive color formation or color change. In a multi-sheet system inwhich an acidic organic polymer is employed, it is desirable to includeother materials to supplement the reactants. For example, kaolin can beadded to improve the transfer of the liquid and/or the dissolvedmaterials between the sheets. In addition, other materials such asbentoni-te, atta-pulgite, talc, feldspar, halloysite, magnesiumtrisilicate, silica gel, pyrophyllite, zinc sulfate, zinc sulfide,calcium sulfate, calcium citrate, calcium phosphate, calcium fluoride,barium sulfate and tannic acid can be included.

Various methods known to the prior art and disclosed in theaforementioned application Ser. No. 392,404 to Miller, et a1. and US.patent application Ser. No. 420,193 to Phillips et al. now US. Patent3,431,494, can be employed in coating compositions of the mark-formingmaterials into their supporting sheets. An example of the compositionswhich can be coated onto the surface of an underlying sheet of atwo-sheet system to react with the capsule coating on the underside ofan overlying sheet is as follows:

Coating composition: Percent by wt.

Phenolic polymer mixture 17 Papr coating kaolin (white) 57 Calciumcarbonate 12 Styrene butadiene latex 4 Ethylated starch 8 Gum arabic 2.

EXAMPLE I Preparation of3-(p-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl) phthalide.

An intermediate keto-acid, 4'-dimethylaminobenzophenone-Z-carboxylicacid was prepared as herein set forth:

A mixture of 14.5 grams of dimethy laniline and 14.8 grams of phthalicanhyd-ride in 30 milliliters of benzene was stirred in a flask underice-cooling. To the mixture,

26.0 grams of anhydrous aluminum chloride was slowly added. Stirring wascontinued at room temperature for 40 minutes and at 55-60 C. for 30minutes. Upon cooling to room temperature, the benzene solvent wasremoved by extraction with petroleum ether, and the residue wasdecomposed with 34 milliliters of 17% sulfuric acid. After partialneutralization with about milliliters of concentrated ammoniumhydroxide, the sulfuric acid solution was diluted with water to a volumeof 900 milliliters and stirred for an additional 30 minutes. Theprecipitate formed was removed by filtration, and exhibited a weight of13.5 grams and a melting point of 195-200 C. The crude intermediate wasrecrystallized from dilute sulfuric acid, thereupon exhibiting a meltingpoint of 200-203 C.

The preparation of 3-(p-dimethylaminophenyl)-3-(1,2--dimethylindol-3-yl) phthalide was effected by the following process:

The keto-acid, prepared in the process set forth above was used in thispreparation. 5.4 grams of 4'-dimethylaminobenzophenone-2-carboxylic acidand 3.2 grams of 1,2dimethylindole were mixed with twenty milliliters ofacetic anhydride. After being heated for fifteen minutes to near theboiling point on a hot plate, the reaction mixture was poured into onehundred milliliters of water and heated for an additional ten minutes.Upon cooling, the mixture was treated with ammonium hydroxide until itwas strongly alkaline, then stirred for ten minutes. The solid whichexhibited a weight of 7.8 grams, was removed by filtration purified byrecrystallization from a benzene solution.

The purified product exhibited a melting point of 226- 228 C. A solutionof the product in benzene turned a vivid blue when applied to a papersheet coated with a phenolic polymer, but imparted a blue-purple colorto paper coated with attapulgite clay.

EXAMPLE II The preparation of 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl) phthalide was effected in the following process:

5 .4 grams of the 4'-dimethylaminobenzophenone-2- carboxylic acidprepared in the foregoing procedure, were mixed with 2.9 grams of2-methylindole and 20 milliliters of acetic anhydride and heated to theboiling point of the mixture on a hot plate for fifteen minutes. Aproduct was isolated according to the procedure described in Example I.The product exhibited a weight of 8.6 grams and was purified byrecrystallization from benzene. The purified product exhibited a meltingpoint of 211-212 C. The color of the product when dissolved in benzeneand reacted with paper coated with phenolic polymer was blue.

EXAMPLE III The compound 3-(p-di-nbutylaminophenyl)13-(1,2-di'methylindol-3-yl) phthalide was prepared in the following procedure:

24.6 grams of di-n-butylaniline, 14.8 grams of phthalic anhydride, and20 milliliters of benzene were stirred in a 100 milliliter flaskimmersed in a cold water bath. 26.7 grams of aluminum chloride wasslowly added, the addition requiring ten minutes. The water bathtemperature was raised to 50 C. in thirty minutes, and maintained at 50C. to 54 C. for one hour. The water bath was removed and the flaskcooled to room temperature. The reaction mixture was then decomposedwith 150 milliliters of 20% sulfuric acid, resulting in the formation ofan oil floating as a supernatant layer. 400 milliliters of water wereadded, causing the oil to change to a semi-solid phase. the aqueoussolution was decanted and the semisolid material was washed twice with400 milliliter quantities of water.

The semi-solid material was then stirred with 1200 milliliters of waterfor one hour. The semi-solid material disintegrated into a light-greencolored precipitate. The water was decanted and fresh water added. Afterthree hours a powdered solid product was percipitated exhibiting aweight of 18.4 grams and a melting point range of 164-168 C. 5 grams ofthe solid intermediate product, 4-di-n-butylaminobenzophenone 2carboxylic acid was dissolved in 50 milliliters of toluene, treated withcharcoal and filtered. A yellow filtrate was treated with an equalvolume of petroleum ether yielding a yellow precipitate exhibiting aweight of 4.7 grams and a melting point range of 168170 C.

1.06 grams of the 4'-di-n-butylaminobenzophenone-Z- carboxylic acidproduct of the foregoing procedure, 0.44 grams of 1,2-dimethylindo1e and10 milliliters of acetic anhydride were heated in a thirty milliliterbeaker to a temperature slightly below the boiling point of the mixturefor 15 minutes. The reaction mixture was poured into milliliters ofwater, made alkaline by the addition of ammonium hydroxide, and stirredfor two hours. A product precipitated which exhibited a weight of 1.3grams. The product, 3-(p-di-n-butylaminophenyl) 3 (1,2dimethylind0l-3-yl) phthalide was dissolved in 30 milliliters ofbenzene, treated with activated charcoal, and filtered. The filtrate wasconcentrated to 5 milliliters and further purified to yield a purifiedproduct exhibiting a weight of 1.05 grams and a melting point range of140-141.5 C. A benzene solution of the product appeared purple whencontacted with attapulgite clay coated on paper and blue when contactedwith phenolic polymer coated on paper.

EXAMPLE IV Preparation of 3-(p-di-nbutylaminophenyl)-3-(2-methylindol-3-yl) phthalide.

3.5 grams of the intermediate4'-di-n-butylaminobenzophenone-2-carboxylic acid, prepared as describedin Example III, 1.3 grams of 2-methylindole, and 25 milliliters ofacetic anhydride were heated to boiling for 15 minutes, poured into 125milliliters of Water, made alkaline with ammonium hydroxide and stirredfor minutes. A precipitate was separated and purified, repeatedly, froma mixture of benzene and petroleum ether. A product thus obtained meltedat 157.5159.5 C. A benzene solution of the product turned a purple colorwhen contacted with attapulgite clay coated on paper but blue whencontacted with a phenolic resin coated on paper.

EXAMPLE V The preparation of 3-(p-dimethylaminophenyl)-3-(2-phenylindol-3-yl) phthalide was effected by the following process:

2.7 grams of 4' dimethylaminobenzophenone 2 carboxylic acid prepared inthe procedure set forth in Example I was mixed With 2.1 grams of2-phenylindole and forty milliliters of acetic anhydride. A crudeproduct, weighing 4.4 grams, was isolated according to the proceduredescribed in Example I. The product was recrystallized from the benezenesolution. The purified product exhibited a melting point of 252-253 C.The benzene solution of the product imparted a green color to papercoated with a phenolic polymer.

EXAMPLE VI The preparation of 3-(p dimethylaminophenyl 3 (1-methyl-Z-phenylindol-3-yl) phthalide was effected by the followingprocedure.

0.8 gram of 4 dimethylaminobenzophenone 2 carboxylic acid prepared inthe procedure set forth in Example I, 0.62 gram of1-methyl-2-phenylindole and 5 milliliters of acetic anhydride werereacted as set forth in Example III. Following the isolation procedureof Example III, a crude product weighing 1.0 gram was obtained uponrecrystallization from 95% ethanol, a pure product exhibiting a meltingpoint range of 146 C. to 148 C. was obtained. A solution in benzene ofthe 3-(pdimethylaminophenyl)-3 (1 methyl-Z-phenylindol-3-yl) phthalideproduct appeared a blue color when reacted with attapulgite clay coatedon paper and appeared green when contacted witha phenolic polymer coatedonto paper. when contacted with a phenolic polymer coated onto paper.

EXAMPLE VII The compound3-(p-diethylaminophenyl)-3-(2-phenylindol-3-y'l) phthalide was preparedin the following procedure:

An intermediate keto-acid 4-diethylaminobenz0phenone-Z-carboxylic acidwas first prepared by stirring 18.0 grams of diethylaniline, 14.8 gramsof phthalic anhydride, and 20 milliliters of benzene in a 100 milliliterflask immersed in a cold water bath. 26.7 grams of aluminum chloride wasslowly added to the reaction mixture, the addition requiring 12 minutes.The water bath temperature was raised to 52 C. over a period of thirtyminutes and maintained at 52-55 C. for 7 minutes. Twenty milliliters ofwater were added, followed by the addition of 200 milliliters of 20%sulfuric acid to the reaction mixture. Upon heating a turbid solutionwas observed. The solution was diluted with water to 800 milliliters andneutralized with ammonium hydroxide to a pH of 1.8. A semi-solid phaseappeared and was separated and stirred into an 800 milliliter quantityof water for 120 minutes. A solid precipitate was formed which exhibiteda weight of 15.7 grams and a melting point range of 173-177 C. The crudematerial was purified by dissolving said material in 4 normal sulfuricacid, filtering the solution to remove insoluble material, andreprecipitating the product with ammonium hydroxide. The melting pointof the 4'-diethylaminobenzophenone-2-carboxylic acid intermediate wasthereby raised to 180181 C.

The intermediate keto-acid prepared in the foregoing procedure was usedin the preparation of the compound 3-(pdiethylaminophenyl)-3-(2-phenylindol-3-yl) phthalide by heating 0.74grams of 4-diethylaminobenzophenone-2-carboxylic acid, 0.48 grams of2-phenylindole and 15 milliliters of acetic anhydride in a beaker over ahot plate for 15 minutes. The reaction mixture was poured into 100milliliters of water, made alkaline with ammonium hydroxide and stirredfor 60 minutes. A crude product exhibiting a weight of 1.1 grams wasprecipitated. The crude product was dissolved in 50 milliliters ofbenzene, treated with charcoal and filtered. The filtrate upon standingyielded a 3-(p-diethylaminophenyl)-3-(2-phenylindo1-3-yl) phthalideproduct exhibiting a melting point of 246247 C. A benzene solution ofthe product appeared a blue-green color when contacted with attapulgiteclay coated on paper and a green color when contacted with a phenolicolymer coated on paper.

12 What is claimed is: 1. A chromogenic compound having the structuralformula where R and R consist of alkyl having from one to four carbonatoms, phenyl, and hydrogen; and Where R and R consist of alkyl havingfrom one to four carbon atoms, and hydrogen.

2. The chromogenic compound of claim 1 where R R R and R are methyl,said compound being 3-(=pdimethylaminophenyl) 3 (1,2 dimethylindol 3-yl) phthalide.

3. The chromogenic compound of claim 1 where R is hydrogen and R R and Rare methyl, said compound being 3 (p dimethylaminophenyl) 3 (2-methylindol-3-yl) phthalide.

4. The chromogenic compound of claim 1 where R and R are methyl and Rand R are n-butyl said com pound being 3 (p di nbutylaminophenyl)-3-(1,2- dimethylindol-3-yl) phthalide.

5. The chromogenic compound of claim 1 where R is hydrogen, R is amethyl, and R5 and R are n-butyl, said compound being 3-(pdi-n-butylaminophenyl)-3-(2- methylindol-3-yl) phthalide.

6. The chromogenic compound of claim 1 Where R is hydrogen, R is aphenyl, and R and R are methyl, said compound being3-(p-dimethylaminophenyl)-3-2- phenylindol-3-yl) phthalide.

7. The chromogenic compound of claim 1 where R is a phenyl, and R R andR are methyl, said compound being 3-(p-dimethylaminophenyl) 3 (1methyl-2- phenylindol-3-yl) phthalide.

8. The chromogenic compound of claim 1 where R is hydrogen, R is aphenyl; and R and R are ethyl, said compound being 3 (pdiethylaminophenyl) 3 (2- phenylindol-3-yl) phthalide.

References Cited UNITED STATES PATENTS 2,505,486 4/1950 Green 260-3433XR ALEX MAZEL, Primary Examiner J. A. NARCAVAGE, Assistant Examiner Us;01. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 491,116 Dated: January 20, 1970 Inventor: Chao-Han Lin It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 3, line 10, 'butylaminophenyl'' should be -buty1aminopheny1)--.Column 6, line 36, "a" should be -an--. Column 8, line 47, "3, 431, 494"should be --3, 455, 721--; line 57, "Papr' should be "Paper-a Column 9,line 56, "13-" should be -3- Column 10, line 5, 'percipitated" should be--preci'pitated-; line 8, "4" should be --4'--; line 61, "benezene'should be --benzene-. Column 11, line 8 should be deleted. Claim 6,

line 3, "3-2" should be 3-(2 SIGNED AN'D SEALED JUL? 1970 (SEAL) Attest:

Edward M. Fletcher, I L

WILLIAM E. 50mm, .13. Ammng Offmer comissioner of Patents

